Bushman, I don't know if that lever is typical of that maker, though I've seen several with the wide lever. I believe the width of the lever is a safety item. When the hammers are all the way back, the rifle cannot be opened because the lever hits the right hammer. It doesn't effect the left hammer, so that the right barrel can be re-loaded while the left hammer is still cocked. This lets the rifle be slammed shut in case the re-load is not completed before the left barrel is needed.

You understand this is only my opinion, and I have no writen documentation to prove that theory!